255/35R21 vs 285/35R20
285/35R20 is 4.0 mm shorter than 255/35R21 in overall diameter (−0.6%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 285/35R20 fitted, the speedometer reads 100 km/h when you are doing 99.4 km/h.
Dimensions side by side
| 255/35R21 | 285/35R20 | |
|---|---|---|
| Overall diameter | 712 mm (28.0″) | 708 mm (27.9″) |
| Section width | 255 mm | 285 mm |
| Sidewall height | 89 mm | 100 mm |
| Rim | 21″ | 20″ |
| Revolutions per km | 447 | 450 |
| In stock | 12 tires from $291.00 | 12 tires from $325.00 |
What changes
- Overall diameter: 285/35R20 is 4.0 mm shorter (−0.6%).
- Speedometer: reads 100 km/h at an actual 99.4 km/h with 285/35R20.
- 285/35R20 is 30 mm wider, so check clearance and the recommended rim width.
- Wheel size changes from 21″ to 20″: you need wheels in the new size.
- Choose a load index at least as high as the one on your door placard.
Vehicles that came with both sizes
Vehicles that use 255/35R21
Vehicles that use 285/35R20
See every alternate size for 255/35R21
Frequently asked questions
Can I use 285/35R20 instead of 255/35R21?
Usually, yes: 285/35R20 is within 3% of the overall diameter of 255/35R21 (−0.6%). Use wheels of the right size and width, match or exceed the original load index, and check clearance at full steering lock.
How much does the speedometer change between 255/35R21 and 285/35R20?
With 285/35R20 instead of 255/35R21, the speedometer shows 100 km/h when you are actually doing 99.4 km/h.
Which vehicles came with both 255/35R21 and 285/35R20?
Both sizes were original equipment, on different trims or packages, on the 2022–2024 Mercedes-Benz S500, 2022–2024 Mercedes-Benz S580, 2024 Mercedes-Benz S580e.